WWI load was the original .30 M1906 Ball ammo- 150 grain cupro-nickel jacketed spitzer at 2700 fps. M1 Ball came later, the heavier boat tailed bullet was wanted to give weapons a longer distance capability- but it came with a price. Heavier recoil was bitched about, overpenetration of backstops at some facilities, and eventually in the late 30's it proved to be too much for the new M1 Garand's gas system/op rods. That precipitated the adoption of Ball M2 which was nothing more nor less the original 1906 load but with a gilding metal jacket.
Armor piercing ammo was issued to frontline rifleman a heckuva lot for reasons of obviously better penetration of stuff.
